Select kqueue for timer on FreeBSD.
Add FreeBSD to conditional compilation that applies to both FreeBSD and MacOSX.
Add missing va_list definition for gcc48/FreeBSD.
Fix stack_t.ss_sp type difference for FreeBSD.
Fix file data syncing for FreeBSD.
Fix build error in javascript driver.

Protoc-js does not always create folder for given output path. We need
to create it explicitly in build procedure.
Fix GCC48 linking error on FreeBSD.
Fix "gmake install" on FreeBSD.

install(1) on FreeBSD does not allow reading file content from
/dev/stdin, so we must create a real file in build directory before
calling install.
Support systems without python in /usr/bin (Ex, FreeBSD).
Add FreeBSD build environment settings.
Add FreeBSD into configure host list.

Tested on FreeBSD 9 with following steps:

 # For dependency
 pkg_add -r wget protobuf protobuf-c v8 openjdk7 boost-all gmake
 pkg_add -r bash node npm py-yaml gcc48
 npm install -g less coffee-script handlebars

 # To configure
 CXX=gcc48 ./configure --ccache
 # Edit config.mk to add "ALLOW_WARNINGS := 1"

 # To build
 gmake